Internet and its related customer services has had an enormous break through during the last decade. Even though the early stages of what has become the Internet of today were almost unknown only ten years ago, at least among ordinary technically oriented people, the Internet of today is virtually known to everyone in the so-called industrialised world. Everyday, the number of people practising and using the Internet is increasing. Many people use it professionally, such as use in offices and laboratories, but also other kinds of use increases rapidly, such as daily use in people's residences.
Customer services developed that are mainly designed for and are well-adapted to new possibilities governed by the Internet have increased at correspondingly fast pace. As a consequence of the increasing possibilities provided by higher data transmission rates and the enhanced image quality and even on-line video over the Internet, to mention just two conceivable applications among many others, a great demand for higher transmission rates has grown among by potential customers, i.e. future subscribers, which has led to a new and currently developing market including significant business opportunities for several involved parties. The customers may for instance be multimedia interested people who want to be able to download real time video or transfer large amounts of data, such as very high resolution images, music files, etc, to and from computers in their homes. A market challenge is to be able to provide high transmission access to the Internet for every customer who is or might become interested.
In order to provide all of these customers with connections supporting very high transmission rates, preferably bi-directional transmission capacity exceeding 2 Mbit per second, which is sometimes called broadband access according to one of a plurality of definitions, a technique allowing for non-problematic mass-installation is required. Prior art, like for instance the European patent application EP 0 981 242 A2, discloses a shared multi-drop ADSL modem allowing for simultaneous connections to at least two local loops. By means of the disclosed invention, two subscribing users may share one single ADSL modem, whereby lower costs associated with the implementation of ADSL modems can be achieved. Furthermore, it is known to use ADSL in combination with split filters with a maintained PSTN/ISDN out-of-band service. However, these split filters are relatively expensive and will not be necessary in a near future when access will be provided in-band. The PSTN/ISDN interfaces will then be on the subscriber side.
However, prior art does not disclose a satisfactory solution to the problem of providing customers a back-up connection in case the installed and activated high speed transmission modem is interrupted by any outer factor or fails. A failing xDSL modem connection may occur for many different reasons, for instance mistakes during installation or activation, instabilities in power distribution, PSTN signal interference in network, etc. In order to achieve sufficient network reliability and thus the customers' full confidence in that their connection is always operable, a solution to the problem of failing xDSL connection is strongly required.